The "CREATIVE RESTORATION" -- BUY-102D
So there you have it. A car must of course have a legitimate title to be registered for license tags for street use. Prior articles discuss lots of numbers you may find on the MGA, and issues of legitimate (legal) title. In the end the only number that really matters (to be legal) is the Car Number stamped on the large ID plate on the heater shelf, and the matching number on the title.
As a matter of reality, it is not unusual for someone to mix, match or swap out almost anything or even everything on the car in the process of restoration. If you happen to have in your possession most of one good MGA with no title, and one legal title (key word is "legal") with no useful car to go with it (presumably parted out or scrapped) you can do some creative restoration work. You could obtain a new ID plate to replace a missing or damaged one, and you can stamp on it the legitimate and legal ID number matching the (presumably legitimate) VIN number on the good title (thereby restoring the damaged or missing ID plate). Thereafter you may attach this plate to the car body of your choice, and place that on the frame of your choice, and attach that to pretty much any combination of parts to reconstruct and restore your car to something resembling the original configuration.
A fairly obvious shortcut in this process is to unscrew the rusted hulk of the old car from the Car No. plate and set it aside. Then move the whole of the donor car underneath and attach it to the Car No. plate as an assembly. Then you go apply for the license plates to put your freshly restored MGA on the street, and you have one very nice and totally legal car. And because it was a legal title to begin with it probably doesn't even have to be inspected, depending on your state of residence (watch out for California).
There are two restrictions that apply here to keep it legal. You must legally own all of the component parts (nothing reported stolen and some reasonable belief of ownership), and you are limited to registering only one car for each legitimate title and Car Number. In other words, the legal ownership goes with the title, and if the car resembles the original issue, everyone's satisfied. There are even a few avenues for legitimizing some possibly questionable title, or for sort of "re-creating" the legal title for a car that might currently have as little as a bill of sale, but I wouldn't elaborate too much unless you have such a need. The point is that it's pretty tough for an MGA with a clear title not to be a certifiably legitimate MG. Just keep repeating to yourself, "It has to be a clear title". Otherwise if you like the car, buy it.
The end result is of course not a concours show car, because the numbers don't match. The process of swapping non-matching parts into a car may have some detrimental affect on the market value of the car. As long as you understand this and price the car accordingly (buyer or seller), everyone should be happy.